Method and means for bonding bearing liners

ABSTRACT

The invention contemplates maintenance of uniform controlled pressure and temperature at the zone of bonding a fabric or the like liner to a bearing ring or the like, the pressure and temperature being at the levels required for optimum curing of the particular thermosetting material involved. The pressure is developed by axial compression of an elastomeric plug, which is so constrained that radial loading of the lining on the bearing element necessarily results from hydrostatic deformation of the plug. The heat supplied for curing also causes the plug to expand, but the invention provides for automatic compensation for plug expansion so as to maintain substantially constant pressure loading on the liner in the course of a curing cycle. Means are disclosed for the bonding of a plurality of lined bearing elements in a single batch processing cycle.

June 6, 1972 METHOD AND MEANS FOR BONDING BEARING LINERS 3,349,94410/1967 Moeller ..220/24.5

Primary Examiner-Carl D. Quarforth [72] Inventor: Gordon J. Clark,Bristol, Conn. Assistant E Lehmann [73] Assignee: Textron Inc.,Providence, R.l. "attorney-Sande Hopgood and Calimafd? [22] Filed: Nov.3, 1969 57] BSTR CT [21] Appl- N -I 373,161 The invention contemplatesmaintenance of uniform controlled pressure and temperature at the zoneof bonding a [52] U s C 156/294 29/149 5 156/272 fabric or the likeliner to a bearing ring or the like, the pres- 1 5 308/239 sure andtemperature being at the levels required for optimum [51] In Cl B52!)31/20 curing of the particular thermosetting material involved. The 58]Fieid 238 pressure is developed by axial compression of an elastomeric 167293 plug, which is so constrained that radial loading of the lining onthe bearing element necessarily results from hydrostatic deformation ofthe plug. The heat supplied for curing also [56] References Cited causesthe plug to expand, but the invention provides for auto- UNITED STATESPATENTS matic compensation for plug expansion so as to maintainsubstantially constant pressure loading on the liner in the course3,184,362 5/1965 LIISky et a1 156/293 UX ofa curing cycle, Means aredisclosed for the bonding f 3,443,716 5/1969 Evans "220/245 rality oflined bearing elements in a single batch processing cy- 3,139,311 6/1964Melton et a1. ..308/238 X 3,387,839 6/1968 Miller et al.. ...308/237 X2,683,875 7/1954 Axelrad ..29/149.5 12 Claims, 8 Drawing Figures PA, 5PE pa ummg 5 a Ely/D su pzy I Z7 METHOD AND MEANS FOR BONDING BEARINGLINERS This invention relates to apparatus and methods for bonding ayieldable liner, such as a low-friction fabric liner, to a rigidsupporting surface, such as the cylindrical bore of a bearing element.

In fabric-lined mechanical devices such as so-called plain bearings,wherein bearing efficacy in large part depends on maintenance of thebond between a fabric and a relatively rigid bearing element, there is aproblem in achieving bonding uniformity, from one bearing to the next,and as between different localized areas of a given bearing. Such lackof uniformity may result in unsatisfactory bearings and is thusobviously wasteful; and product quality cannot be relied upon ifhigh-performance specifications must be met. Litsky U.S. Pat. No.3,l84,362 discloses a method of applying heat and pressure to cure thebond, utilizing differential thermal expansion coefficients of analuminum slug in a lined steel ring, but this technique has been foundto have limitations, particularly in the circumstance of dimensionalvariations within tolerance limitations that apply to bore size, fabricbulk, and aluminum slug diameter.

It is, accordingly, an object to provide an improved method andapparatus avoiding or materially reducing the noted difficulties anddeficiencies.

A specific object is to provide a method and apparatus for developingbonds of the character indicated, with greater uniformity and of highquality, from one specimen to the next, and throughout the bonded areaof any particular specimen.

A further specific object is to provide an improved method and apparatusof the character indicated, particularly adapted to efficient massproduction of bonded articles.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred methods and apparatus of the invention:

FIG. 1 is an enlarged vertical sectional view to illustrate an articlein readiness for processing by the method and apparatus of theinvention;

FIG. 2 is a view similar to FIG. l'to show the article after processingaccording to the invention;

FIG. 3 is a diagrammatic sectional view on a reduced scale toschematically illustrate apparatus of the invention;

FIG. 4 is a similar diagrammatic view to schematically indicate furtherdetail of the apparatus;

FIG. 5 is a vertical sectional view to illustrate modified apparatus;

FIG. 6 is an exploded fragmentary perspective view to illustrate anotherembodiment of the invention;

FIG. 7 is a view similar to FIG. 1 but directed to the embodiment ofFIG. 6; and

FIG. 8 is a fragmentary sectional view of a lined bearing element, toillustrate a result achieved by the method and apparatus of theinvention.

Briefly stated, the invention contemplates maintenance of uniformcontrolled pressure and temperature at the zone of bonding a fabric orthe like liner to a bearing ring or the like,

the pressure and temperature being at the levels required for optimumcuring of the particular thermosetting material involved. The pressureis developed by axial compression of an elastomeric plug, which is soconstrained that radial loading of the lining on the bearing elementnecessarily results from hydrostatic deformation of the plug. The heatsupplied for curing also causes the plug to expand, but the inventionprovides for automatic compensation for plug expansion so as to maintainsubstantially constant pressure loading on the liner in the course of acuring cycle. Means are disclosed for the bonding of a plurality oflined bearing elements in a single batch processing cycle. 1

FIGS. 1 and 2 show an illustrative article, being a ring 10,respectively before and after processing in accordance with theinvention. The ring 10 is a relatively rigid element of a socalled plainbearing, which relies upon a fabric liner 11 to sustain a radial loadwith respect to a shaft (not shown) slidably positioned by the liner 1].The ring 10 may be a straight cylindrical annulus as shown, in whichcase the final lined-bore diameter D accommodates a suitably matchedcylindrical shaft surface. In another employment, the ring 10 maysuitably ductile to undergo swaging, as to a concave spherical boreshape, after the liner 11 has been bonded to the cylindrical bore shown;for such a swaging operation, the undeformed ring periphery may beundulated as suggested by phantom outline 10', to provide sufficient endmaterial for producing the deformed ends and at the same time to yield asubstantially right-cylindrical outer surface after deformation.

The liner 11 may be one of a' variety of weaves, braids, and fibercombinations depending on use requirements. Generally, forself-lubricating low-friction purposes, the fabric of liner 11preferably provides Teflon (tetrafluoro-ethylene) fibers at least at thebearing surface. The fabric 11 may be presoaked with uncured (orincompletely cured) thermosetting resin such as a phenolic, and suchresin may incorporate adhesive intended ultimately to complete the bondto the ring bore; alternatively, a thermosetting adhesive, such as aphenolicbased adhesive, may be applied as a preliminary coat, either tothe ring bore or to the outer surface of fabric liner 1 1.Alternatively, a thermoplastic adhesive, or a combined thermosetting andthermoplastic adhesive may be used.

In accordance with the invention, an elastomeric plug 12 of diameter D(less than the ultimate lined-ring diameter D is inserted into axialoverlap with the bore or ring 10 and with the uncured fabric liner 1].The undeformed axial extent W of the plug 12 exceeds the axial extent Wof the liner 1], the latter extent being also the width of the bearingring 10. The thus preliminarily assembled parts are placed between upperand lower platens 13-14, which will be understood to form part of apress for axially compressing the plug 12, thereby achievingradiallyoutward uniform compression of the liner 1 I over the surface of thering bore. Such pressure, and heat, are maintained for the curinginterval, at the conclusion of which the platens are separated to allowplug restoration to the unstressed state, whereupon the bonded article(lined ring 10-1 1) is removed from the plug and from the press.

FIG. 3 schematically illustrates heating means 15-16 carried by therespective platens 131 4,and the platens 13-14 are sufficientlyextensive to embrace a spaced plurality of preliminarily assembledrings, liners and plugs 12. The heating means 15-16 is shown to beelectrical, governed by a single control means 17, with provision at 18for manual selection of a desired controlled-heat level, as monitored bya feedback connection 19 which includes a heat-sensitive element 20carried by one of the platens. The heavy arrow 21 suggests means todownwardly displace the upper platen 13, for developing the indicatedcompression of all plugs 12in the batch which is being processed.

FIG. 4 supplies further detail as to an illustrative means fordownwardly displacing the upper platen l3 and for providing controlledpressure loading of the liners in the respective ring bores,throughout'the bonding (curing) interval. The platendisplacementmechanism is shown to include a hydraulic cylinder 23 with a piston-rodconnection 24 to the upper platen 13. Pressure fluid from a suitablesource is supplied to the head end of cylinder 23 via a regulator 25having manual means 26 for selection of a desired delivery pressure tobe maintained in the outlet line 27 to cylinder 23. If desired, anindicator 28 may track the delivered pressure, by connection to thefeedback line 29 which governs regulator action. The platen-positioningmechanism will be understood to include further means (not shown) forretracting platen 13 to relieve plug compression and to permitfinished-part removal.

In use, the material of plug 12 is selected from the varioushigh-temperature elastomers which have thermal capability to meetcurrent adhesive bonding requirements. I have found it satisfactory toemploy a fluorinated elastomer by the name VITON-A, being a product ofBL duPont de Nemours & Co.; such an elastomer is eminently satisfactoryfor temperatures in the order of 375 F., as used in the curing ofphenolics. On the other hand, should the thermoset material be apolyimide, in which case bonding temperatures are in the order of 550 Fl have found it Satisfactory to employ a silicone rubber by the nameSilastic, being a product of Dow-Chemical Co.

GenerallyQthe undeformed plug diameter may match the preliminarilyassembled liner and ring, with a clearance in the order of one mil, andthe amount by which the axial extent of plug l2 exceeds the axial extentof the liner 1] may be in the order of a few thousandths of an inch.

Platen pressure applied by means 23-25 radially compresses the liner 11to the ring bore, at a level selected at 26. The heated platens causeplug 12 to expand against the regulated pressure loading at 23, so thateven if this expansion involves upward displacement of platen 13, theradial load on the linerremains substantially constant throughout thecuring cycle. I

FIG. illustrates a slight modification wherein spaced like boredrecesses 30-31-32 in the lower platen l4 serve to locate the plugs 12used in batch curing of bonded liners. In certain cases, it maybeconvenient to assemble plugs 12 first to the recesses 30-31-32, andthen to assemble liners and rings to the plugs 12. In other situations,it may be more convenient to preassemble the plugs 12 with their linersand rings, prior to mounting the preassemblies at the locating recesses30-31-3 2. In either event, uniform spacing of bonding regions isreadily achieved with the arrangement of FIG. 5.

FIGS. 6 and 7 illustrate use of the invention in the bonding of a fabricstrip or liner 40 to the outer cylindrical surface 41 of a bearingelement or ring 42. In this situation, the adhesive is inside the fabricand the elastomeric plug 43 is annular and is outside the fabric. Axialcompression of plug 43 is translated into radial compression of theliner 40 to cylindrical surface 41 by circumferentially constrainingtheplug 43. In the form shown, spaced bores 44-45 in the upper face of thelower platen 46 accommodate the plugs 43, as with a l-mil clearance foreasy insertion; and, as with the previously described embodiment, theaxial extent of the plug (43) exceeds the axial extent of the liner(40). Stated in other words, the plug 43 projects sufficiently, or theplatens 46-47 are otherwise suitably configurated,to permit the desiredplug compression prior to platen interference with each other or withring 42.

lt will be seen that the invention provides greater flexibility inapplication of bonding pressure during the curing cycle. Bond strengthbetween the fabric and the cylindrical surface to which it is'bonded isdifficult to evaluate; however, tests in-, dicate bond integrity atleast as good if not better than that obtainable with aluminum plugsunder the best conditions. This result is achieved with plugs for 'whichdimensioning is not critical, as in the case of the diameter of analuminum plug. Moreover, unlike the aluminum plug, the elastomeric pluglends itself to uniformly distributed application of radial pressure andto ready conformation of the liner to a chamfer or other edgeconfiguration of the cylindrical surface to be lined; such a conformedlining appears at 50 in the case of a lined chamfered bore, in FIG. 8.

The method of the invention achieves the foregoing advantages while alsosimplifying the heating process, by eliminating the need for ovencuring, since heated platens do not require an oven. Moreover, largebatches may be cured under like, regulated, conditions of elevated heatand pressure, in spite of plug expansion due to heat.

Although the invention has been described in detail for the methods andapparatus shown, it will be understood that modifications may be madewithout departing from the invention.

What is claimed is:

l. The method of bonding a' flexible liner to the cylindrical bore of arigid bearing ring, which comprises preliminarily asadhesive material atthe ring-liner interface, selecting a cylindrical plug of elastomericmaterial of diametral extent to clear the preliminarily lined bore ofthe ring and of axial extent exceeding the axial extent of the liner,axially inserting the plug into overlap with the liner, applying axialcompression to the plug to radially squeeze the liner to the bore of thering, heating the plug, and maintaining a predetermined elevated heatedand pressurized state of the plug for a predetermined period ofadhesive-curing time. i v

2. The method of claim 1, wherein the selected plug is of siliconerubber. I

3. The method of claim 1, wherein the selected plug is ofhigh-temperature fluorinated elastomeric material.

4. The method of claim 1, wherein the liner is a fabric having fibers oftetrafluoroethylene exposed at the inner surface thereof.

5. The method of bonding a yieldable low-friction bearing liner to arigid bearing element having a cylindrical surface to be lined, whichcomprises selecting liner material of size to circumferentially andaxially fit said cylindrical surface with thermosetting adhesivematerial at the interface of said liner with said cylindrical surface,selecting a plug of elastomeric material having a cylindrical surfacewhich radially clears said liner and the cylindrical surface of thebearing element when axially overlapped therewith, said plug being ofaxial'extent exceeding the axial extent of the liner, preliminarilyassembling the plug and liner and bearing elementjnto axial overlap,compressing the plug to radially squeeze the liner to the cylindricalsurface of the bearing element, heating the plug, and maintaining apredetermined elevated heated and pressurized state of the plug for apredetermined period of adhesive-curing time.

6. The method of claim 5, wherein said plug is cylindrical and saidbearing element is a ring surrounding said plug.

7. The method of claim 5, wherein said plug is annular and thecylindrical surface of said bearing element is' received within saidplug.

8. The method of claim 7, wherein the compression of the plug isachieved by axially compressing the plug while rigidly confining theouter circumference of the plug.

9. The method of bonding a fabric liner to the bore of a rigid bearingring, utilizing a pair of opposed platens, which comprises preliminarilyassembling the liner to the bore of the ring with thermosetting materialat the ring-liner interface, said thermosetting material being in astage less than fully cured, selecting a cylindrical plug of elastomericmaterial of diametral extent to fit the preliminarily lined bore of thering and of axial extent exceeding the axial extent of the ring, axiallyinserting the plug into overlap with the ring and liner, placing theplugged ring between the platens with the ends of the plug facing therespective platens, drawing the platens together to axially compress theplug and thus radially compress the liner to the ring bore, heating atleast one of said platens to heat the plug and achieve curingtemperature in the thermosetting material, and maintaining apredetermined elevated heated and pressurized state of the plug for apredetermined period of curing time for the thermosetting material.

10. The method of claim 9, in which plural like assemblies of pluggedlined rings are placed in laterally spaced relation between the platens,so that plural lined rings may be bonded in a given heat-and-pressurecuring cycle of the platens.

11. The method of claim 1, in which said flexible liner includes a wovenfabric material.

12. The method of claim 1, wherein the bore of the ring includes achamfer at one end, and wherein the plug and liner are assembled inaxial overlap with the chamfer, whereby the liner is bonded to thechamfer as well as to the rest of the lined part of the bore.

2. The method of claim 1, wherein the selected plug is of siliconerubber.
 3. The method of claim 1, wherein the selected plug is ofhigh-temperature fluorinated elastomeric material.
 4. The method ofclaim 1, wherein the liner is a fabric having fibers oftetrafluoroethylene exposed at the inner surface thereof.
 5. The methodof bonding a yieldable low-friction bearing liner to a rigid bearingelement having a cylindrical surface to be lined, which comprisesselecting liner material of size to circumferentially and axially fitsaid cylindrical surface with thermosetting adhesive material at theinterface of said liner with said cylindrical surface, selecting a plugof elastomeric material having a cylindrical surface which radiallyclears said liner and the cylindrical surface of the bearing elementwhen axially overlapped therewith, said plug being of axial extentexceeding the axial extent of the liner, preliminarily assembling theplug and liner and bearing element into axial overlap, compressing theplug to radially squeeze the liner to the cylindrical surface of thebearing element, heating the plug, and maintaining a predeterminedelevated heated and pressurized state of the plug for a predeterminedperiod of adhesive-curing time.
 6. The method of claim 5, wherein saidplug is cyLindrical and said bearing element is a ring surrounding saidplug.
 7. The method of claim 5, wherein said plug is annular and thecylindrical surface of said bearing element is received within saidplug.
 8. The method of claim 7, wherein the compression of the plug isachieved by axially compressing the plug while rigidly confining theouter circumference of the plug.
 9. The method of bonding a fabric linerto the bore of a rigid bearing ring, utilizing a pair of opposedplatens, which comprises preliminarily assembling the liner to the boreof the ring with thermosetting material at the ring-liner interface,said thermosetting material being in a stage less than fully cured,selecting a cylindrical plug of elastomeric material of diametral extentto fit the preliminarily lined bore of the ring and of axial extentexceeding the axial extent of the ring, axially inserting the plug intooverlap with the ring and liner, placing the plugged ring between theplatens with the ends of the plug facing the respective platens, drawingthe platens together to axially compress the plug and thus radiallycompress the liner to the ring bore, heating at least one of saidplatens to heat the plug and achieve curing temperature in thethermosetting material, and maintaining a predetermined elevated heatedand pressurized state of the plug for a predetermined period of curingtime for the thermosetting material.
 10. The method of claim 9, in whichplural like assemblies of plugged lined rings are placed in laterallyspaced relation between the platens, so that plural lined rings may bebonded in a given heat-and-pressure curing cycle of the platens.
 11. Themethod of claim 1, in which said flexible liner includes a woven fabricmaterial.
 12. The method of claim 1, wherein the bore of the ringincludes a chamfer at one end, and wherein the plug and liner areassembled in axial overlap with the chamfer, whereby the liner is bondedto the chamfer as well as to the rest of the lined part of the bore.